The present invention is directed to decorative glass, and more specifically to annealed glass sheets of the type described in which a plurality of parallel, adjacent grooves are ground into at least one surface thereof for a distinctive visual effect.
In recent years the interior and exterior design of buildings and structures, as well as the furnishings therefor, have employed increasing quantities of decorative glass. For example, it is now commonplace for glass sheets to be used in various types of doors such as shower doors, storm doors, patio doors, entry doors, bi-fold doors, and in decorative windows, mirrors, and other furniture and architectural applications as the scope of architectural and design tastes expand, the industry has become receptive to glass sheet products which have unique visual effects.
One such visual effect is achieved by the use of a ground groove in the surface of such glass products. The groove is formed by grinding into the surface of an annealed glass sheeting,, however, the glass sheets may subsequently be bent, or curved, or further processed (such as by tempering).
Heretofore, it has been commonplace to bevel the side edges of a sheet of glass before emplacing , within a frame or using it as a window, mirror, table top, or table top decoration. Beveling is accomplished essentially by relative movement between the sheet of glass and one or more grinding wheels whose surface is tilted at a small angle with respect to the surface of the glass. There are some instances where a grinding wheel, which normally has a flat peripheral surface, has been formed with a V-shaped surface to grind a single, wide, shallow groove in a sheet of glass (commonly referred to as "V-grooving"). The grinding step often is followed by polishing to clear the surface. The width of the peripheral surface of conventional grinding wheels is commonly in the range of 10 millimeters to 20 millimeters. Therefore, such V-grooves known heretofore have been essentially at least 10 millimeters in width and very shallow. The purpose of V-grooves as described hereinabove has been to simulate panels of glass in a larger sheet without use of individual panes and associated framework. As a result, very little refraction or reflection occurs and no striking visual difference between the grooved section and the plain section is achieved.
In accordance with the present invention, a different and striking visual effect is achieved by forming a plurality of narrow, parallel grooves or ribs with sharper angles. Such grooves have steeper walls, thereby achieving more extreme refraction and/or reflection results, more distortion, and therefore a more striking visual difference between the ribbed or grooved section and the other surface of the glass sheet. It was found that there was no existing satisfactor, technique to grind multiple, parallel, adjacent, narrower grooves in the surface of a sheet of glass. One way to accomplish such a result with equipment available, which has been used in the past on wider grooves with shallower angles, to subject the glass in a single pass to a Successive plurality of grinding and polishing wheels, each offset along the length of the path of travel of the glass sheet. As the workpiece passes by the grinding wheels, each wheel forms one groove. The alternative approach is to run the glass sheet past the same grinding wheel for a plurality of passes with the sheet being moved laterally after each pass. Polishing occurs in the same manner with a different wheel. First of all, because of the configuration of known grinding wheels, such grooves have to be very shallow. Additionally, when each groove is formed separately, it is extremely difficult to achieve and maintain precise alignment of the grinding wheels, so that the grooves are formed parallel to each other. A slight misalignment essentially ruins the parallel arrangement and results in a reject. Also the machine must be slowed down considerably.
Thus, to accomplish the desired visual effect, it is necessary to devise a different approach to form the ribbed pattern of the present invention. Here, as is different from conventional glass sheet grinding techniques, there is provided a plurality of parallel adjacent grooves in the surface of the sheet of glass, each of the grooves having a maximum width dimension of approximately 7 millimeters and a minimum angle between the grooved wall and the plane of the plate glass surface of 12.degree.. In a preferred technique, the grooves are rough cut, then finish cut and polished during a single pass of the glass sheet along a horizontal path through a grinding machine. Such a machine includes a rough cut diamond wheel, one or more finishing cut diamond wheels, and one or more polishing wheels rotating about a horizontal axis. Alternatively, while the workpiece is held stationary, a rough cut grinding wheel is passed along the surface in a prescribed path to form all grooves or ribs simultaneously. Next, a finish cut grinding wheel is passed along the surface in the same or similar manner, followed by polishing with one or more polishing wheels. In each of the aforesaid techniques, the grinding surface of each of the grinding wheels includes a plurality of parallel adjacent grooves formed in the periphery thereof, the grooves being substantially the mirror image of the groove pattern to be formed on the glass. By altering the normal flat surface of the diamond grinding wheel and by providing a grooved surface therein on a rough cut wheel and a finishing cut wheel, the plurality of grooves can be formed simultaneously, which assures that they are parallel and remain in relative alignment with each other.
The resulting grooves in the surface of the glass sheet are much narrower, and may have side walls with a sharper angle from the plane of the glass surface. This results in a significant difference in the visual effect observed from one side of the glass sheet in light passing from the opposite side or in light reflected in the case of a mirror. The emerging light rays from the walls of the groove are bent at a more extreme angle, and therefore the diffusion or distortion is significantly more remarkable. As a result, the visual effect is substantially different between the grooved section and the non-grooved section.
Further, in accordance with the invention, it has been determined that each of the plurality of grooves should have a maximum width dimension of 7 millimeters. It is desired that the depth of the cut be as deep as possible without adversely affecting the strength and integrity of the glass sheet beyond acceptable standards. In order to obtain a good scattering of light as a result of the refraction caused by the side walls of the grooves, the minimum angle between the groove wall and the plane of the glass surface is approximately 12.degree.. Such parameters permit the grinding of grooves in glass sheets having thicknesses in the range of one-eighth to one inch.
A preferred method which has been developed for forming the grooved glass sheet of the present invention starts with the dressing (or forming) of the grinding wheel surface to provide the desired groove configuration. First a rough cut diamond particle wheel is formed in which the peaks and valleys are somewhat rounded. It is very difficult to grind a flat piece of glass into a precise grooved configuration in a single cut because, when a large quantity of glass is removed, it is difficult to maintain close tolerances. Therefore, it is preferable to first subject the workpiece to a rough cut diamond grinding wheel which roughs out the approximate shape of the grooved configuration, then subject the glass to one or more downstream finishing cut grinding wheels, which form the finer, more precise cut to complete the grooved configuration. This is followed by one or more polishing wheels. The two wheels are then mounted sequentially on a horizontal grinding machine and sheets of glass are passed therebeneath on a conveyor belt. The sheet of glass must be first fixed to the conveyor, then the grooves can be simultaneously rough cut and simultaneously finish cut during a single pass. Alternatively, the grooved configuration may be formed by holding the workpiece stationary and moving one or more grooved grinding wheels and polishing wheels to form the patterns of multiple grooves.
It is therefore an object of the present invention to provide a decorative glass sheet having a unique decorative visual effect.
It is another object of the present invention to provide a decorative glass sheet having a plurality of narrow, parallel, adjacent grooves in at least one surface thereof.
It is still another object of the present invention to provide a technique and tool for forming the decorative glass of the present invention wherein all grooves in a groove configuration are formed simultaneously.